From the same rule you quoted:
There is literally no justification ICly, as a non antag, for stealing weapons on code green. To add to that, breaking into a secure weapons armory is nowhere near considered 'minor criminal activity'. I don't think I need to explain why that's not 'minor criminal activity'.
While not everything in the armory is an antagonist objective (the ablative vest is) stealing guns and other such important items also falls under this little bit. Whereas engineering can just print off, say, a welding tool if you stole that, security cannot quite so easily secure additional energy weapons without at least a three minute time limit, factoring in the time it would take to order and collect items from cargo, if other complications don't arise in the process.
Weapons are also used in emergency situations. If anything requiring lethal force attacks, you've just screwed security in most scenarios, especially during code green when security isn't usually armed to the teeth already.